RoleoftheMitochondrialPeptideHumanininRegulatingAgingandStressResistance Aging and longevity are regulated by multiple pathways, but two of the most potent regulators of the aging process are diet and the GH/IGF axis, which are themselves inter-related. Over the last funding period we studied the effects of dietary interventions and GH/IGF-axis modulation on longevity and diseases of aging, and we have also identified a remarkable relationship between these interventions and the novel mitochondrial-derivedpeptide,humanin,whichisencodedfromasmallopenreadingframe(sORF)withinthe mitochondrial genome (16S rRNA gene). Dietary restriction (DR), GH/IGF reduction, and H2S lead to increases in humanin levels, while humanin suppresses IGF-I and dramatically raises the levels of IGFBP-1. Humanin levels fall with age and humanin overexpression or administration to various organisms leads to healthspan and lifespan extension. Similarly to DR, humanin protects from a variety of insults, and its administration prevents the development of diseases of aging. These studies suggest a DR-mimetic role for humanin. In this project we will consider the central hypotheses that (1) humanin is a DR-mimetic whose expression is regulated by aging-modulating interventions such as dietary manipulations, H2S, and IGF- reduction, and (2) humanin administration can act similarly to DR and periodic fasting or protein restriction cycles(PFC,PRC),H2S,andGH/IGF-blockade,topromotelongevityandhealthspan. We will study the mechanisms by which diet, IGF, and H2S regulate humanin expression;? and study the transcriptionalandpost-transcriptionalregulationofthehumanin-sORF.Wewillproposetodemonstrateusing several mouse models and in vitro systems that humanin treatment or over-expression delays aging and aging-related diseases acting as a physiological DR-mimetic (and that humanin knock-down has opposite effects)andelucidatethemechanismsinvolved,includingIGF-1suppressioninhepatocytes.Together,these proposed studies will demonstrate the dietary-restriction-like effects of humanin and will advance our understandingofitsregulationbydietandGHanditsmechanismsofaction.Ifsuccessful,ourworkwillsetthe stageforclinicaladvancementofnewdiagnosticandtherapeuticinterventionsfordiseasesofaging.